As the island begins to sink under the ocean, Hank (Dwayne "The Rock" Johnson) and Sean (Josh Hutcherson) dive under the water and find Captain Nemo's old submarine, the Nautilus, in a cave. They attempt to start it up, but find that its batteries are dead. Hank connects a cable to a harpoon and "jump starts" the submarine by spearing a giant electric eel, and using the eel's electricity to power the ship. Gabato (Luis Guzman) pilots the submarine to safety.
A year later, we see that Gabato's daughter Kailani (Vanessa Hudgens) is attending college in the USA, where she lives with Sean, Hank and Liz. Gabato is making a fortune taking toruists for rides in the Nautilus.
Sean's Grandfather Alexnder (Michael Caine) comes to their home for Sean's birthday (an occasion he'd missed many times in the past). He brings along texts suggesting that they may attempt a trip to the moon in the next sequel, as Jules Verne described in the novel "From the Earth to the Moon."
Thanks John L!